TW201718398A - Method for producing hydrogen chloride - Google Patents

Abstract

Provided is a method for producing hydrogen chloride that makes it possible to produce hydrogen chloride efficiently using simple equipment. Hydrogen chloride is produced using a method that comprises: a gas-liquid contact step in which an inert gas is brought into gas-liquid contact with hydrochloric acid having a concentration of 20-50 mass%, inclusive; a separation step in which crude hydrogen is obtained by distilling the hydrochloric acid with which the inert gas is brought into gas-liquid contact in the gas-liquid contact step and separating hydrogen chloride from the hydrochloric acid; a dehydration step in which the crude hydrogen obtained in the separation step is dehydrated; and a refinement step in which the dehydrated crude hydrogen obtained in the dehydration step is compressed and liquefied and the liquid crude hydrogen is refined through distillation.

Description

Method for producing hydrogen chloride

The present invention relates to a method for producing hydrogen chloride.

High-purity hydrogen chloride (HCl) used as an etching gas, a scrubbing gas, or a film-forming gas used in the production of a semiconductor or the like is obtained, for example, by liquefying hydrogen chloride obtained by using a synthetic hydrochloric acid as a raw material, and then removing impurities by distillation. In the manufacturing method, impurities are greatly different in distillation, and since the boiling point of hydrogen bromide (HBr) and carbon dioxide (CO ₂ ) in the impurities is close to hydrogen chloride, it is not easily removed by distillation, and it is necessary to have a larger Problems such as the size of the distillation column.

Patent Document 1 discloses a technique in which a hydrogen chloride gas containing hydrogen bromide is passed through an aqueous hydrogen chloride solution saturated with hydrogen chloride to obtain a hydrogen chloride gas having a reduced hydrogen bromide content. However, the technique disclosed in Patent Document 1 has a problem that it is difficult to achieve a level of impurity concentration required for producing a high-purity hydrogen chloride gas for semiconductor use in recent years, for example, to reduce the content of hydrogen bromide to about 0.2 ppm by volume.

Further, Patent Document 2 discloses a technique in which chlorine (Cl ₂ ) and hydrogen (H ₂ ) are each purified in advance to produce high-purity hydrogen chloride. The chlorine is refined by removing carbon dioxide by distillation. However, in the technique disclosed in Patent Document 2, in order to preliminarily purify chlorine and hydrogen, it is necessary to provide a distillation column and an adsorption tower to complicate the production equipment of high-purity hydrogen chloride, and it is difficult to efficiently produce high-purity hydrogen chloride.

Prior technical literature Patent literature

Patent Document 1: Japanese Patent Publication No. 2142 of 2004

Patent Document 2: Japanese Patent Publication No. 545704, 2013

In order to solve the problems of the prior art described above, an object of the present invention is to provide a method for efficiently producing high-purity hydrogen chloride with a simple apparatus.

In order to solve the above problems, one aspect of the present invention is as described in the following [1] and [2].

[1] A method for producing hydrogen chloride, which comprises a gas-liquid contact step of bringing a concentration of 20% by mass or more and 50% by mass or less of hydrochloric acid into an air-liquid contact with an inert gas, and a step of separating the hydrochloric acid obtained by gas-liquid contact with the inert gas in the gas-liquid contacting step, separating the hydrogen chloride from hydrochloric acid to obtain crude hydrogen chloride, a dehydration step of dehydrating the crude hydrogen chloride obtained in the separating step, and compressing the dehydration step After the dehydrated crude hydrogen chloride is liquefied, the liquid crude hydrogen chloride is purified by distillation.

[2] The method for producing hydrogen chloride according to [1], wherein the gas-liquid contacting step is performed by using an inert gas with a linear velocity of 0.1 m/h or more and 15 m/h or less and a space velocity of 0.1/h or more and 10 The flow rate of hydrochloric acid at a flow rate of /h or less is reversed, and the reaction of the hydrochloric acid gas liquid with the inert gas is performed, and the ratio of the volume flow rate of the inert gas to the volume flow rate of hydrochloric acid is 0.01 or more and 100 or less.

The invention can produce high-purity hydrogen chloride efficiently and conveniently.

10‧‧‧buffer tank

15‧‧‧Carbon Diffusion Tower

20‧‧‧Distillation tower

30‧‧‧Condenser

40‧‧‧Water adsorption tower

50‧‧‧Compressor

60‧‧‧Distillation tower

Fig. 1 is a schematic view showing a manufacturing apparatus of high-purity hydrogen chloride in the method for producing high-purity hydrogen chloride of Example 1.

Fig. 2 is a schematic view showing a manufacturing apparatus of high-purity hydrogen chloride in the method for producing high-purity hydrogen chloride of the second embodiment.

Form of implementing the invention

In order to solve the above-mentioned problems, the inventors of the present invention have intensively reviewed and found that after hydrogen chloride and an inert gas are brought into gas-liquid contact, hydrogen chloride is separated by hydrochloric acid by distillation, whereby impurities can be easily produced efficiently by means of equipment (for example, boiling point is similar to hydrogen chloride and it is difficult to borrow The present invention has been completed by hydrogen chloride having a lower content of hydrogen bromide and carbon dioxide which are removed by distillation. An embodiment of the present invention will be described in detail below.

The method for producing hydrogen chloride according to the present embodiment includes a gas-liquid contact step of bringing a concentration of 20% by mass or more and 50% by mass or less of hydrochloric acid into contact with an inert gas in a gas-liquid contact, and a step of contacting the distillate gas with the inert gas. a step of separating hydrochloric acid obtained by gas-liquid contact and separating hydrogen chloride from hydrochloric acid to obtain crude hydrogen chloride, liquefying the dehydrated step of dehydrating the crude hydrogen chloride obtained in the separation step, and dehydrating the crude hydrogen chloride obtained by the compression dehydration step, followed by distillation A step of purifying the crude crude hydrogen chloride in the form of a liquid.

In the method for producing high-purity hydrogen chloride of the present embodiment, the hydrochloric acid used as the raw material is an aqueous solution having a concentration of hydrogen chloride of 20% by mass or more and 50% by mass or less. When the concentration of hydrogen chloride is 20% by mass or more and 50% by mass or less, for example, the gas obtained from the top of the column when the hydrochloric acid is distilled in a distillation column contains abundant hydrogen chloride. When the concentration of hydrogen chloride is less than 20% by mass, the gas obtained from the top of the column cannot contain abundant hydrogen chloride because it does not have a concentration of hydrogen chloride equal to or higher than the azeotropic composition. Further, since hydrochloric acid having a concentration of hydrogen chloride exceeding 50% by mass exceeds the saturated solubility of hydrogen chloride at normal temperature and atmospheric pressure, it is generally not used. Further, hydrochloric acid having a hydrogen chloride concentration of 40% by mass or less is preferably used under normal temperature and atmospheric pressure conditions.

In the present embodiment, the impurities in the hydrogen chloride are particularly important for hydrogen bromide and carbon dioxide, and the reason for the mixing is hydrochloric acid for the raw material. The concentration of hydrogen bromide in the general synthetic hydrochloric acid is usually 1 ppm by mass or more and 100 ppm by mass or less, and the concentration of carbon dioxide is usually 0.01 ppm by mass or more and 5 ppm by mass or less. As described above, even if hydrogen chloride obtained by synthesizing hydrochloric acid in the previous method is distilled to produce high-purity hydrogen chloride, it is difficult to sufficiently remove hydrogen chloride and carbon dioxide at a boiling point similar to hydrogen chloride.

The gas-liquid equilibrium constant (K-value=[CO ₂ ]gas phase/[CO ₂ ]liquid phase) of carbon dioxide in the liquefied hydrogen chloride obtained by carbon dioxide was experimentally 1.3, and the separation efficiency under gas-liquid was poor due to the closeness to 1. However, since the state of hydrochloric acid is an aqueous solution, carbon dioxide is easily removed from hydrochloric acid by contact with gas and liquid of an inert gas. Therefore, by using the hydrochloric acid obtained by removing carbon dioxide, for example, high-purity hydrogen chloride having a low concentration of carbon dioxide as low as 0.4 ppm by volume can be produced.

In the gas-liquid contact step in the method for producing hydrogen chloride according to the present embodiment, an inert gas such as nitrogen (N ₂ ), argon or helium is brought into gas-liquid contact with hydrochloric acid. The method of contacting the gas and liquid of the inert gas with hydrochloric acid is not particularly limited, but it is preferably carried out by a countercurrent contact method in which hydrochloric acid flows from the upper side to the lower side and the inert gas flows from the lower side to the upper side in terms of efficiency.

The preferable conditions for bringing the hydrochloric acid into contact with the inert gas in gas-liquid contact may vary depending on the structure of the apparatus to be used, the concentration of hydrochloric acid, etc., and cannot be generalized, but it is preferably a temperature of 0 ° C or more and 60 ° C or less and a pressure of 0.01 MPa. Above 1 MPa (absolute pressure).

Further, the flow rate of the hydrochloric acid and the inert gas in the gas-liquid contact was investigated by the inventors, and it was found that the gas-liquid contact can be more effectively removed by gas-liquid contact under the following conditions. Further, the gas-liquid contact of the hydrochloric acid with the inert gas may be continuous or batchwise.

That is, it is preferable that the flow rate of hydrochloric acid is a linear velocity of 0.1 m/h or more and 15 m/h or less, a space velocity of 0.1/h or more and 10/h or less, and a ratio of a volume flow rate of an inert gas to a volume flow rate of hydrochloric acid is 0.01. Above 100 or less. The linear velocity of hydrochloric acid is preferably 0.1 m/h or more and 15 m/h or less, more preferably 1 m/h or more and 10 m/h or less, and more preferably 1.5 m/h or more and 7 m/h or less. Further, the space velocity of hydrochloric acid is preferably 0.1/h or more and 10/h or less, more preferably 0.1/h or more and 5/h or less, and more preferably 0.2/h or more and 3/h or less. Further, the ratio of the volume flow rate of the inert gas to the volume flow rate of hydrochloric acid is preferably 0.01 or more and 100 or less, more preferably 0.1 or more and 50 or less, still more preferably 1 or more and 40 or less.

When the flow rate of hydrochloric acid is 0.1 m/h or more and 15 m/h or less and the space velocity is 0.1/h or more and 10/h or less, carbon dioxide can be sufficiently removed from hydrochloric acid by contact with a gas-liquid of an inert gas, and may have The efficiency is obtained in a sufficient amount to remove carbon dioxide from hydrochloric acid.

Further, when the flow rate of the inert gas is such that the ratio of the volume flow rate of the inert gas to the volume flow rate of hydrochloric acid is 0.01 or more and 100 or less, carbon dioxide can be sufficiently removed by hydrochloric acid by contact with the gas-liquid of the inert gas. It is generally estimated that the higher the flow rate, the higher the removal efficiency of carbon dioxide, but in fact the flow rate of the inert gas is less affected by the removal efficiency of carbon dioxide. Therefore even if the volume flow rate relative to hydrochloric acid is not The ratio of the volume flow rate of the active gas is greater than 100. In addition to the inability to further enhance the removal efficiency of carbon dioxide, hydrochloric acid may be lost with the splash of hydrochloric acid. The ratio of the volume of the inert gas to the volume of hydrochloric acid in the batch mode is preferably 0.1 or more and 100 or less, and the gas-liquid contact time at this time is preferably 3 minutes or more and 300 minutes or less.

Secondly, the gas-liquid equilibrium constant (K-value=[HBr]gas phase/[HBr]liquid phase) of hydrogenated hydrogen chloride in the liquefied hydrogen chloride obtained by hydrogen bromide is 0.8, which is close to 1 and therefore separated by gas and liquid. Poor efficiency. However, the concentration of hydrogen bromide in the hydrogen chloride after evaporation was measured, and the concentration of hydrogen bromide in the hydrogen chloride and the concentration of hydrogen bromide in the residue were determined to obtain a gas-liquid equilibrium constant of hydrogen bromide in hydrochloric acid, and the result was 0.2. Therefore, it is known that there is a large difference in the behavior of hydrogen bromide in the liquefied hydrogen chloride.

That is, it was found that it is difficult to sufficiently separate hydrogen bromide when distilling hydrogen chloride, but it is easy to separate hydrogen bromide when distilling hydrochloric acid. Further, in the present embodiment, crude hydrogen chloride is obtained by diffusing hydrogen chloride with hydrochloric acid by heating and introducing an inert gas, and crude hydrogen chloride is obtained by distilling hydrochloric acid. In other words, in the method for producing hydrogen chloride according to the present embodiment, hydrochloric acid obtained by gas-liquid contact with the inert gas in the distillation gas-liquid contact step in the separation step is separated from hydrogen chloride to obtain crude hydrogen chloride.

The hydrochloric acid for distilling the raw material may be continuously or batchwise, but it is preferably carried out in a continuous manner. The method of introducing hydrochloric acid into the distillation column can be appropriately selected in accordance with continuous or batchwise distillation of hydrochloric acid. In the continuous mode, hydrochloric acid is continuously introduced into the distillation column. When the hydrochloric acid is introduced into the distillation column, the separation efficiency of hydrogen bromide by distillation and the efficiency of distilling off the concentration of hydrochloric acid diluted by distillation of hydrogen chloride from the top are prevented, preferably the distillation column is high. The direction is near the central part.

The crude hydrogen chloride having a lower hydrogen bromide concentration can be obtained from the distillation column by distilling hydrochloric acid, and the hydrochloric acid having a higher content of hydrogen bromide and having a dilute concentration by distilling hydrogen chloride from the bottom of the distillation column is distilled off. The distribution ratio of hydrogen bromide can be determined by the value of the gas-liquid equilibrium constant (for example, 0.2) and the number of stages of the distillation column. The concentration of hydrochloric acid distilled from the bottom of the distillation column is not particularly limited, but is preferably an azeotropic concentration under the pressure of distillation conditions and 20% by mass under atmospheric pressure.

The operating pressure at which the hydrochloric acid is distilled in the separation step is such that the concentration of the azeotropic hydrogen chloride at the operating pressure is lower than the concentration of the hydrogen chloride supplied to the distilled hydrochloric acid. The operating pressure values that meet this type of condition are determined by the relationship between the concentration of hydrogen chloride in hydrochloric acid and the concentration of azeotropic hydrogen chloride and pressure. When distillation is carried out under an operating pressure such that the azeotropic hydrogen chloride concentration is equal to or higher than the hydrogen chloride concentration of the raw material hydrochloric acid, the fraction obtained from the top of the column is mixed with a large amount of hydrogen bromide with water. Further, when distillation is carried out at an operating pressure lower than the concentration of hydrogen chloride of the raw material hydrochloric acid under the operating pressure, it is possible to prevent the crude hydrogen chloride from having a low hydrogen bromide concentration by distilling off the water from the top.

The distillation operation pressure of hydrochloric acid is preferably selected from the range of 0.1 MPa or more and 0.5 MPa or less (absolute pressure). When the hydrochloric acid is distilled under such operating pressure, the load of the distillation apparatus is not increased, and a sufficient amount of crude hydrogen chloride can be obtained. When the distillation is carried out under reduced pressure, the concentration of hydrogen chloride in the azeotropic composition can be increased, so that the amount of hydrogen chloride obtained is not preferable.

Further, the distillation operation temperature of hydrochloric acid (the temperature at the bottom of the distillation column) depends on the operating pressure or the like, but is generally 100 ° C or more and 150 ° C or less.

Further, the form of the distillation column is not particularly limited, and a packed tower or a shed can be used. A distillation column generally used for a tower or the like is preferred, but a packed column having a simple structure is preferred. For the filling of the packed tower, known things such as Raschig rings, Boer rings, Traray (registered trademark), and the like can be used.

Next, in the method for producing hydrogen chloride according to the present embodiment, the dehydration step is carried out by dehydrating the crude hydrogen chloride obtained in the separation step, and the dehydration method is not particularly limited. For example, a method in which a carrier is contacted with a crude hydrogen chloride in an absorber filled with a carrier such as activated alumina or zeolite, a method of removing water by crude hydrogen chloride by adsorption of a carrier, or a method of cooling crude hydrogen chloride to condense moisture. Further, the above method of using a carrier and a method of condensing moisture can be combined.

In the method for producing hydrogen chloride according to the present embodiment, for example, the crude hydrogen chloride dehydrated in the dehydration step is compressed and liquefied at a pressure of 2.6 MPa (absolute pressure) or more at a temperature of about 0 ° C, and then the liquid is purified by distillation. Crude hydrogen chloride gives high purity hydrogen chloride. The distillation apparatus used in the refining step may be one which has a function required for general distillation, and is preferably a rectification apparatus (distillation column) using a shed column or a packed column. However, it is better to use a packed tower with a simple structure. For the filling of the packed tower, known things such as Raschig rings, Boer rings, Traray (registered trademark), and the like can be used. Further, the distillation may be carried out continuously (continuous distillation) or in a batchwise manner (batch distillation).

The operating conditions for distilling hydrogen chloride may be various depending on the practicality and the required quality of hydrogen chloride, and the like, and are not particularly limited. However, in the case where the temperature at the top of the distillation column is not too low, the operating pressure may be 0.1 MPa or more and 10 MPa or less, preferably 0.5 MPa or more and 5 MPa or less. Under such operating conditions, the top temperature of the distillation column can be about -80 ° C. Above 60 ° C. When the distillation is carried out under the above conditions, the low-boiling component can be taken out from the top of the column, and the high-boiling component can be taken out from the bottom, and high-purity hydrogen chloride can be obtained from the middle of the distillation column.

According to the method for producing hydrogen chloride of the present embodiment, it is possible to efficiently produce, for example, high-purity hydrogen chloride having a purity of 99.999 mass% or more. The high-purity hydrogen chloride produced can be used, for example, as an etching gas or a scrubbing gas in the production of a semiconductor or a thin film transistor. In particular, in the crystal epitaxial growth step of Si-Ge (semiconductor), GaN (light-emitting diode, etc.), or SiC (power semiconductor), it can be used as a film forming gas in addition to a cleaning gas, but impurities may exist in the film forming gas. Since the impurities remain in the film, the high-purity hydrogen chloride obtained by the method for producing hydrogen chloride of the present embodiment is extremely useful. In addition, high-purity hydrogen chloride can also be used to manufacture various chemicals such as medical supplies, dye intermediates, and the like.

Further, the present embodiment is an example of the present invention, and the present invention is not limited to the embodiment. Further, the present embodiment can be variously modified or improved, and such modifications or improvements are also included in the present invention.

Example

The invention will now be described in more detail by way of examples.

[Example 1]

High purity hydrogen chloride was produced using the manufacturing apparatus shown in FIG. The raw material hydrochloric acid to be used was a product having a hydrogen chloride concentration of 35% by mass and a hydrolyzate containing 70 ppm by mass of impurities and 2 ppm by mass of carbon dioxide.

Hydrochloric acid was introduced into the buffer tank 10 having a capacity of 1000 kg by a hydrochloric acid introduction pipe 11 at a flow rate of 580 kg/h. Next, with respect to the hydrochloric acid in the buffer tank 10, nitrogen is introduced through the inert gas introduction pipe 12 at a flow rate of 600 NL/h, and foaming is performed at a normal temperature (gas-liquid contact step).

Hydrochloric acid was continuously introduced into the buffer tank 10 at a flow rate of 580 kg/h to continuously bubble nitrogen, and hydrochloric acid was continuously discharged from the buffer tank 10 at a flow rate of 580 kg/h, and liquid was fed into the distillation column 20 through the hydrochloric acid liquid supply pipe 21. Inside. At this time, the ratio of the volume flow rate of the inert gas to the volume flow rate of hydrochloric acid was 1.3.

In the distillation column 20, hydrochloric acid after gas-liquid contact with an inert gas is distilled under the conditions of a pressure of 0.1 MPaG and a temperature of 115 ° C, and hydrogen chloride is separated by hydrochloric acid (separation step). Crude hydrogen chloride was discharged from the top of the column of the distillation column 20 at a flow rate of 93 kg/h, and hydrochloric acid diluted by distilling hydrogen chloride was discharged from the bottom of the distillation column 20 at a flow rate of 487 kg/h.

The hydrogen chloride concentration of the crude hydrogen chloride discharged from the top of the column was 96% by volume, the concentration of hydrogen bromide in the impurity was 0.2 ppm by volume, and the concentration of carbon dioxide was 10 ppm by volume. Further, the concentration of hydrogen chloride discharged from the bottom portion was 23% by mass, the concentration of hydrogen bromide in the impurity was 83 ppm by mass, and the concentration of carbon dioxide was 1 ppm by mass.

Since the crude hydrogen chloride discharged from the top of the column of the distillation column 20 contains water, it is sent to the condenser 30 and the moisture adsorption tower 40 for dehydration (dehydration step). That is, the crude hydrogen chloride is supplied into the condenser 30 from the distillation column 20 by the hydrogen chloride piping 31, and is cooled to -5 ° C to condense the water in the crude hydrogen chloride to remove a part of the moisture in the crude hydrogen chloride.

In addition, the crude hydrogen chloride is sent to the moisture adsorption tower 40 by the condenser 41 through the hydrogen chloride charging pipe 40, and is adsorbed by the adsorbent (Mooreqiu 3A, manufactured by Unicorn Showa Co., Ltd.) which is filled in the moisture adsorption tower 40. Thereby, the crude hydrogen chloride after dehydration can be obtained at a flow rate of 90 kg/h. The crude hydrogen chloride after dehydration had a hydrogen chloride concentration of 99.9% by volume and contained 13 ppm by volume of impurity carbon dioxide.

The dehydrated crude hydrogen chloride is sent to the compressor 50 by the moisture adsorption tower 40 by the hydrogen chloride charging pipe 40, and is compressed by the compressor 50 by 2.6 MPa or more (absolute pressure) to be condensed (liquefied). The crude hydrogen chloride liquefied by the compressor 50 is sent to the distillation column 60 by the hydrogen chloride pipe 61, and the low-boiling component and the high-boiling component are removed by distillation, and high-purity hydrogen chloride is taken out from the middle of the distillation column (refining step).

Specifically, first, in order to remove a trace amount of the heavy metal component, the high boiling component is discharged from the bottom at a flow rate of 9.0 kg/h, and then discharged from the top of the column at a flow rate of 1.8 kg/h, and the carbon dioxide content is 520 ppm by volume. A low boiling component of 99% by volume of hydrogen chloride.

Thereby, high-purity hydrogen chloride having a purity of 99.999 mass% or more can be obtained from the middle portion of the distillation column 60 at a flow rate of 79 kg/h. The concentration of the impurities contained in the obtained high-purity hydrogen chloride was measured, and as a result, hydrogen bromide was 0.2 ppm by volume and carbon dioxide was 1.8 ppm by volume.

[Embodiment 2]

High purity hydrogen chloride was produced using the manufacturing apparatus shown in FIG. The method for producing high-purity hydrogen chloride of Example 2 is that, in addition to the gas-liquid contacting step, It is almost the same as the production method of the high-purity hydrogen chloride of Example 1. Further, the raw material hydrochloric acid used was the same as that of Example 1. 2, the same or corresponding portions in FIG. 2 are given the same reference numerals as in FIG. 1.

The hydrochloric acid of the raw material is introduced into the carbon dioxide diffusion column 15 through the hydrochloric acid introduction pipe 16, and nitrogen is introduced into the nitrogen introduction pipe 17 to carry out countercurrent contact (gas-liquid contact step). The carbon dioxide diffusion tower 15 has a size of 500 mm in diameter and a height of 6 m in the column, and has a packed bed filled with a filler.

In the carbon dioxide diffusion tower 15, hydrochloric acid flows from the upper side to the lower side, and nitrogen flows from the lower side to the upper side, and the both flow in the countercurrent contact. The flow rate of hydrochloric acid was 382 kg/h (volume flow rate 324 NL/h, linear velocity LV = 1.7 m/h, space velocity SV = 0.28/h), and nitrogen flow rate was 13.4 kg/h (volume flow rate 10.7 Nm ³ /h). Therefore, the ratio of the volume flow rate of the inert gas to the volume flow rate of hydrochloric acid is 33.

From the top of the carbon dioxide diffusion tower 15, nitrogen was discharged with the loss of 4 kg/h of hydrochloric acid, and hydrochloric acid was discharged from the lower side at a flow rate of 378 kg/h. The hydrogen chloride concentration of the discharged hydrochloric acid was 35 mass%, the concentration of hydrogen bromide in the impurity was 70 mass ppm, and the concentration of carbon dioxide was 0.05 mass ppm.

Hydrochloric acid which is in gas-liquid contact with the inert gas in the carbon dioxide diffusion column 15 is sent to the distillation column 20 through the hydrochloric acid liquid supply pipe 21, and is distilled under the atmospheric pressure in the distillation column 20 at a temperature of 110 ° C. Hydrogen chloride is separated (separation step).

The top of the column of the distillation column 20 was discharged with a crude hydrogen chloride at a flow rate of 61 kg/h, and a hydrochloric acid having a diluted concentration by distilling off hydrogen chloride was discharged from the bottom of the distillation column 20 at a flow rate of 317 kg/h.

The hydrogen chloride concentration of the crude hydrogen chloride discharged from the top of the column of the distillation column 20 was 96% by volume, the concentration of hydrogen bromide in the impurity was 0.2 ppm by volume, and the concentration of carbon dioxide was 0.4 ppm by volume. Further, the concentration of hydrogen chloride discharged from the bottom portion was 23% by mass, the concentration of hydrogen bromide in the impurity was 83 ppm by mass, and the concentration of carbon dioxide was 1 ppm by mass.

Since the crude hydrogen chloride discharged from the top of the column of the distillation column 20 contains water, dehydration (dehydration step) is performed by the condenser 30 and the moisture adsorption tower 40 in the same manner as in the first embodiment. Thereby, the crude hydrogen chloride after dehydration can be obtained at a flow rate of 59 kg/h. The hydrogen chloride concentration of the crude hydrogen chloride after dehydration was 99.9% by volume.

The dehydrated crude hydrogen chloride is sent to the compressor 50 by the moisture adsorption tower 40 by the hydrogen chloride charging pipe 40, and is compressed by the compressor 50 by 2.6 MPa or more (absolute pressure) to be condensed (liquefied). The liquefied crude hydrogen chloride is sent to the distillation column 60 by the compressor 50 by the hydrogen chloride pipe 61, and the low-boiling component and the high-boiling component are removed by distillation, and high-purity hydrogen chloride is taken out from the middle of the distillation column (refining step).

In detail, first, in order to remove a trace amount of heavy metal components, a high boiling component is discharged from the bottom at a flow rate of 6 kg/h, and then discharged from the top of the column at a flow rate of 0.4 kg/h, containing a carbon dioxide content of 10 ppm by volume. A low boiling component of 99% by volume of hydrogen chloride.

Thereby, high-purity hydrogen chloride having a purity of 99.999 mass% or more can be obtained from the middle of the distillation column 60 at a flow rate of 52.6 kg/h. The concentration of the impurities contained in the obtained high-purity hydrogen chloride was measured, and as a result, hydrogen bromide was 0.2 volume ppm, and carbon dioxide was 0.4 volume ppm.

[Example 3]

High-purity hydrogen chloride was produced in the same manner as in Example 2 except that the size of the carbon dioxide diffusion column 15 was changed to a diameter of 500 mm and a column height of 1 m. Since the size of the carbon dioxide diffusion tower 15 is different, the space velocity SV of the flow rate of hydrochloric acid in the gas-liquid contact step is 1.7 / h.

As a result, high-purity hydrogen chloride having a purity of 99.999 mass% or more can be obtained from the distillation column 60 at a flow rate of 52.6 kg/h. The concentration of the impurities contained in the obtained high-purity hydrogen chloride was measured, and as a result, hydrogen bromide was 0.2 ppm by volume and carbon dioxide was 1.1 ppm by volume.

[Example 4]

High-purity hydrogen chloride was produced in the same manner as in Example 2 except that the size of the carbon dioxide diffusion column 15 was changed to a diameter of 250 mm and a column height of 6 m. Since the size of the carbon dioxide diffusion tower 15 is different, the linear velocity LV of the flow rate of hydrochloric acid in the gas-liquid contact step is 6.6 m/h, and the space velocity SV is 1.1/h.

As a result, high-purity hydrogen chloride having a purity of 99.999 mass% or more can be obtained from the distillation column 60 at a flow rate of 52.6 kg/h. The concentration of the impurities contained in the obtained high-purity hydrogen chloride was measured, and as a result, hydrogen bromide was 0.2 ppm by volume and carbon dioxide was 1.5 ppm by volume.

[Comparative Example 1]

Same as in the first embodiment except that the content of the separation step is changed as described below. Produce hydrogen chloride. That is, the separation step of Example 1 was carried out by separating hydrogen chloride from hydrochloric acid to obtain crude hydrogen chloride by distilling hydrochloric acid, but the separation step of Comparative Example 1 was carried out by using a hydrochloric acid diffusion column instead of the distillation column 20 by simply heating hydrochloric acid to dilute hydrogen chloride with hydrochloric acid. Crude hydrogen chloride. The hydrochloric acid diffusion tower uses a material having a packed bed filled with a filler. The diffusion conditions were a column bottom temperature of 110 ° C and atmospheric pressure.

As a result, hydrogen chloride having a purity of 99.998 mass% or more was obtained from the distillation column 60 at a flow rate of 79 kg/h. The concentration of the impurities contained in the obtained hydrogen chloride was measured, and as a result, hydrogen bromide was 4 ppm by volume and carbon dioxide was 1.8 ppm by volume.

[Comparative Example 2]

Hydrogen chloride was produced in the same manner as in Example 1 except that the hydrochloric acid of the raw material was directly introduced into the distillation column 20 to carry out distillation without performing the gas-liquid contact step.

As a result, hydrogen chloride having a purity of 99.998 mass% or more was obtained from the distillation column 60 at a flow rate of 79 kg/h. The concentration of the impurities contained in the obtained hydrogen chloride was measured, and as a result, hydrogen bromide was 0.2 volume ppm, and carbon dioxide was 10 volume ppm.

15‧‧‧Carbon Diffusion Tower

16‧‧‧ hydrochloric acid introduction tube

17‧‧‧Nitrogen introduction tube

20‧‧‧Distillation tower

21‧‧‧ Hydrochloric acid pipe

30‧‧‧Condenser

31‧‧‧Pipe for hydrogen chloride

40‧‧‧Water adsorption tower

41‧‧‧Pipe for hydrogen chloride

50‧‧‧Compressor

51‧‧‧Pipe for hydrogen chloride

60‧‧‧Distillation tower

61‧‧‧Pipe for hydrogen chloride

Claims (2)

A method for producing hydrogen chloride, which comprises a gas-liquid contact step of bringing a concentration of 20% by mass or more and 50% by mass or less of hydrochloric acid into an air-liquid contact with an inert gas, and performing the gas-liquid contact step with the inert gas. a step of separating crude hydrogen chloride by separating hydrochloric acid from hydrochloric acid after contact with hydrochloric acid, and a step of dehydrating the crude hydrogen chloride obtained by the above-mentioned separation step, and liquefying the crude hydrogen chloride obtained by the dehydration step, by liquefying A step of purifying the liquid crude hydrogen chloride by distillation. The method for producing hydrogen chloride according to claim 1, wherein the gas-liquid contacting step is performed by using an inert gas with a linear velocity of 0.1 m/h or more and 15 m/h or less and a space velocity of 0.1/h or more and 10/h or less. The hydrochloric acid is subjected to countercurrent contact, and the step of bringing the hydrochloric acid into gas-liquid contact with the inert gas, and the ratio of the volume flow rate of the inert gas to the volume flow rate of hydrochloric acid is 0.01 or more and 100 or less.